Although it is not a single cause, a study led by Antonio Rosas, researcher at the Higher Council for Scientific Research (CSIC), reveals that high inbreeding could be relevant in the extinction of Neanderthals. For the research, published in the scientific journal "Scientific Reports", the team analyzed the fossil remains of the 13 Neanderthals recovered in the Asturian cave of El Sidrón, all members of the same family. Researchers have detected up to 17 congenital anomalies that can be seen throughout the skeleton of these paleolithic humans. These genetic singularities have been found in the nose, jaw, ribs, foot and wrist, among other parts of the body.
"The extinction of the Neanderthals was probably due to a combination of ecological and demographic factors that includes interaction with modern humans. In particular, the Neanderthals lived in small groups and geographically separated from each other, so they were practically isolated. The result is that they began to cross between members of the same family and, with the passage of time, in addition, the group was further reduced and inbreeding increased. This inbreeding, maintained over time, could lead to a significant decrease in Neanderthal biological variability ", highlights Antonio Rosas.
The study of the family group of El Sidrón composed of 13 individuals has revealed up to 17 congenital anomalies distributed throughout the skeleton. All of them shared by several members of the group. The group consisted of seven adults (four women and three men), three teenagers and three children. "An example of this is that at least four of the 13 Neanderthals of El Sidrón had an anomaly in the closure of the anterior or posterior arch of the cervical vertebrae. Another striking case is the presence of anomalies of congenital character in the scaphoid (one of the bones of the wrist), "explains Luis Rios, the first signatory of the article, who works with the Paleoanthropology Group of the National Museum of Natural Sciences of the CSIC.
In some cases the researchers have only recovered small remains of bones from one of the 13 Neandertals, which makes it impossible to study all the congenital anomalies that could have each of the Neanderthals of El Sidrón. For this reason, it is not ruled out that these and other singularities could have been repeated in more individuals of the Asturian group.
"These osteological findings are the first to support the general picture emerging from Neanderthal paleogenetics. In this sense, studies conducted in various samples, including those of El Sidrón, indicate high levels of inbreeding, maintained over time, and with a possible increase in the last Neanderthal groups that survived, "says Ríos.
The information obtained from the Neanderthals of El Sidrón agrees with the genetic studies of the fossil remains of other European Neanderthals, such as those of the Croatian cave of Vindija and those of Altai, in Siberia. According to the results, in both cases there was also inbreeding. In Altai, in addition, there was consanguinity, that is, there were offspring between half-brothers.
The 13 of El Sidrón: the Neanderthal family
The fossils of the El Sidrón cave, in Piloña (Asturias), represent the most complete and abundant collection of Neanderthal remains from the Iberian Peninsula. During the excavation work, carried out between 2000 and 2013, more than 2,500 skeletal remains were recovered from at least 13 Neanderthal individuals who lived there approximately 49,000 years ago.
Among the remains are four jaws, three jaws, a multitude of teeth, cranial fragments and different bones of the trunk and limbs. In the El Sidrón cave, a multidisciplinary team of researchers has been working for years, composed of the paleoanthropologist Antonio Rosas (National Museum of Natural Sciences of the CSIC), the CSIC geneticist Carles Lalueza-Fox (Institute of Evolutionary Biology, CSIC mixed center and Pompeu Fabra University) and the archaeologist Marco de la Rasilla (University of Oviedo).
The analysis of Neanderthal skeletal remains from El Sidrón has made it possible to draw many conclusions about the life of these prehistoric human communities. Evidence has been found that they divided the work by sexes, that they knew the medicinal use of certain plants, that their diet included mushrooms, pine nuts and moss and that they would have practiced cannibalism.